Method and apparatus for controlling a DC/DC converter

ABSTRACT

A control system including a DC/DC converter and a control module. The DC/DC converter includes a first inductor and a second inductor. The DC/DC converter is configured to i) receive a first DC voltage and ii) output a second DC voltage. The control module is configured to, during a first operation mode, charge the first inductor while discharging the second inductor, and, during a second operation mode, one of i) charge the first inductor while charging the second inductor and ii) discharge the first inductor while discharging the second inductor. The control module is further configured to initiate the second operation mode in response to detecting a current transient in the DC/DC converter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/710,384 (now U.S. Pat. No. 7,679,347), filed on Feb. 23, 2007, whichis a continuation of U.S. patent application Ser. No. 10/890,491 (nowU.S. Pat. No. 7,190,152), filed on Jul. 13, 2004, and relates to U.S.patent application Ser. No. 10/621,058 (now U.S. Pat. No. 7,161,342),filed on Jul. 15, 2003, entitled “Low Loss DC/DC Converter”, U.S. patentapplication Ser. No. 10/754,187, filed on Jan. 8, 2004, which is acontinuation-in-part of U.S. patent application Ser. No. 10/693,787,filed on Oct. 24, 2003, and U.S. patent application Ser. No. 10/810,452,filed on Mar. 26, 2004. The disclosures of the above applications areall hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to DC/DC converters, and more particularlyto digital control systems for DC/DC converters.

BACKGROUND OF THE INVENTION

DC/DC converters are electronic devices that employ inversion and/orrectification to transform DC voltage at a first level into DC voltageat a second level. For example, a DC/DC converter may step-up DCvoltage, step-down DC voltage, or may be capable of both stepping up andstepping down DC voltage. DC/DC converters typically include one or moreinductors. Inductors are circuit elements that operate based on magneticfields. The source of the magnetic field is charge that is in motion, orcurrent. If current varies with time, the magnetic field that is inducedalso varies with time. A time-varying magnetic field induces a voltagein conductors that are linked by the magnetic field.

Referring to FIG. 1A, a DC/DC converter 10 includes an inductor 12.Inductors 12 in DC/DC converters 10 typically communicate with at leastone switch and at least one capacitor. For example, the switch may be atransistor and the capacitor may be an output capacitor that filters anoutput voltage of the DC/DC converter 10. A control module maycommunicate with the switch to control when the inductor 12 charges ordischarges. For example, when the switch is on, the input current mayflow through the switch and inductor 12 to the capacitor while buildingup the magnetic field of the inductor 12. When the switch is off, theinductor 12 opposes the drop in current and supplies current to thecapacitor.

Referring now to FIGS. 1B and 1C, one or more conductors form coupledinductor circuits 14 and 16, respectively. In FIG. 1B, first and secondconductors pass through the same magnetic core and exhibit mutualcoupling with a coupling coefficient that is approximately equal to 1.In FIG. 1C, a single conductor passes through the magnetic core two ormore times and exhibits mutual coupling with a coupling coefficient thatis approximately equal to 1. Those skilled in the art can appreciatethat still other inductor circuits may be employed. In FIGS. 1B and 1C,the coupled inductor circuits 14 and 16 are implemented in DC/DCconverters 18 and 20, respectively. DC/DC converters 18 and 20 thatemploy coupled inductor circuits 14 and 16 have a fast response withsmall voltage ripple and high efficiency.

Control modules in DC/DC converters generate control signals to turn theswitches on an off and to adjust a rate at which the inductors chargeand discharge. The control signals typically have fixed frequencies andduty cycles to obtain predetermined output voltages. However, when thecontrol module maintains control signals at a fixed frequency and dutycycle, the control module is unable to adapt to changing circuitconditions.

SUMMARY OF THE INVENTION

A closed-loop control system for a DC/DC converter according to thepresent invention includes a DC/DC converter that receives a first DCvoltage and that generates a second DC voltage. The DC/DC converterincludes first and second inductances. A control module communicateswith the DC/DC converter, receives the second DC voltage, and generatesat least one control signal to one of charge or discharge the first andsecond inductances. The control module has first and second modes.During the first mode the control module alternately charges one of thefirst and second inductances and discharges the other of the first andsecond inductances. During the second mode the control module one ofcharges or discharges both of the first and second inductances.

In other features, the control module initiates the second mode when atransient condition occurs in the DC/DC converter. The control moduledetects the transient condition when the second DC voltage is one ofgreater than a first predetermined voltage or less than a secondpredetermined voltage. During the second mode the control moduleinitiates the first mode when the second DC voltage is both less thanthe first predetermined voltage and greater than the secondpredetermined voltage. The control module discharges both of the firstand second inductances when the second voltage is greater than the firstpredetermined voltage. The control module charges both of the first andsecond inductances when the second DC voltage is less than the secondpredetermined voltage.

In still other features of the invention, the DC/DC converter includesan output capacitance. The control module detects the transientcondition when current through the output capacitance is one of greaterthan a first predetermined current or less than a second predeterminedcurrent. During the second mode the control module initiates the firstmode when the current is less than the first predetermined current andgreater than the second predetermined current. The control modulecharges both of the first and second inductances when the current isless than the second predetermined current. The control moduledischarges both of the first and second inductances when the current isgreater than the first predetermined current. The control moduledetermines the current based on a rate of change of the second DCvoltage. The current is one of greater than the first predeterminedcurrent or less than the second predetermined current when the rate ofchange is greater than a predetermined rate of change. The controlmodule determines the current based on an average value of the second DCvoltage during a predetermined time period.

In yet other features, during the second mode the control moduleinitiates the first mode after a predetermined time period. The DC/DCconverter includes an output capacitance. The output capacitancedischarges when the control module discharges both of the first andsecond inductances. The DC/DC converter includes an output capacitance.The output capacitance charges when the control module charges both ofthe first and second inductances.

In still other features of the invention, the DC/DC converter includesfirst, second, third, and fourth switches. Second terminals of the firstand third switches communicate with first terminals of the second andfourth switches, respectively. First terminals of the first and thirdswitches communicate. Second terminals of the second and fourth switchescommunicate. A first end of the first inductance communicates with thesecond terminal of the third switch and the first terminal of the fourthswitch. A first end of the second inductance communicates with thesecond terminal of the first switch and the first terminal of the secondswitch. Second ends of the first and second inductances communicate. Acapacitance has a first end that communicates with the second ends ofthe first and second inductances and a second end that communicates withthe second terminals of the second and fourth switches.

In yet other features, the first, second, third, and fourth switchescomprise transistors. The control module generates first, second, third,and fourth control signals that communicate with control terminals ofthe first, second, third, and fourth switches, respectively. The controlmodule asserts the third and fourth control signals to charge the firstinductance and the first and second control signals to charge the secondinductance. The first DC voltage is input to the first terminals of thefirst and third switches. The second DC voltage is referenced from thefirst end of the capacitance. The DC/DC converter includes a currentsource. A first end of the current source communicates with the secondend of the first and second inductances and the first end of thecapacitance and a second end of the current source communicates with thesecond terminals of the second and fourth switches and the second end ofthe capacitance.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1A is a functional block diagram and electrical schematic of aninductor implemented in an exemplary DC/DC converter according to theprior art;

FIG. 1B is a functional block diagram and electrical schematic of acoupled inductor circuit with two conductors implemented in an exemplaryDC/DC converter according to the prior art;

FIG. 1C is a functional block diagram and electrical schematic of acoupled inductor circuit with one conductor implemented in an exemplaryDC/DC converter according to the prior art;

FIG. 2 is a functional block diagram and electrical schematic of acoupled-inductor DC/DC converter with a control module that implementsan open-loop control system according to the present invention;

FIG. 3 is a timing diagram that illustrates the control signal waveformsgenerated by the control module of FIG. 2 including alternating chargingand discharging of the first and second inductors;

FIG. 4 is a functional block diagram of a closed-loop control system fora DC/DC converter;

FIG. 5 is a graph showing the output voltage of the DC/DC converter inFIG. 4 as a function of time;

FIG. 6 is a timing diagram that illustrates the control signal waveformsgenerated by the control module of FIG. 4 including an overlap of thecharging pattern for the first and second inductors;

FIG. 7 is an electrical schematic of the closed-loop DC/DC controlsystem of FIG. 4;

FIG. 8 is a flowchart illustrating steps performed by the control moduleof FIGS. 4 and 7 including initiating same-phase operation of the firstand second inductors for a predetermined time period; and

FIG. 9 is a flowchart illustrating steps performed by the control moduleof FIGS. 4 and 7 including initiating same-phase operation of the firstand second inductors while a variable is outside of a predeterminedrange.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. For purposes of clarity, the same referencenumbers will be used in the drawings to identify similar elements. Asused herein, the term module refers to an application specificintegrated circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group) and memory that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

Referring now to FIG. 2, an open-loop control system 28 for a DC/DCconverter 30 includes a control module 32. The DC/DC converter 30includes first, second, third, and fourth transistors 34, 36, 38, and40, respectively. Sources (or second terminals) of the first and thirdtransistors 34 and 38, respectively, communicate with drains (or firstterminals) of the second and fourth transistors 36 and 40, respectively.Drains of the first and third transistors 34 and 38, respectively,communicate and sources of the second and fourth transistors 36 and 40,respectively, communicate.

First and second inductors 42 and 44, respectively, form a coupledinductor circuit 46. A first end of the first inductor 46 communicateswith the source of the third transistor 38 and the drain of the fourthtransistor 40. A first end of the second inductor 44 communicates withthe source of the first transistor 34 and the drain of the secondtransistor 36. Second ends of the first and second inductors 42 and 44,respectively, communicate. A first end of a capacitor 48 communicateswith the second ends of the first and second inductors 42 and 44,respectively.

A second end of the capacitor 48 communicates with the sources of thesecond and fourth transistors 36 and 40, respectively. A first end of acurrent source 50 communicates with the first end of the capacitor 48and the second ends of the first and second inductors 42 and 44,respectively. A second end of the current source 50 communicates withthe sources of the second and fourth transistors 36 and 40,respectively, and the second end of the capacitor 48. A input DC voltage52 (V_(in)) of the DC/DC converter 30 communicates with the drains ofthe first and third transistors 34 and 38, respectively. An output DCvoltage 54 (V_(out)) of the DC/DC converter 30 in referenced from thesecond ends of the first and second inductors 42 and 44, respectively,the first end of the capacitor 48, and the first end of the currentsource 50.

The control module 32 generates first, second, third, and fourth controlsignals U₂, D₂, U₁, and D₁ that communicate with gates (or controlterminals) of the first, second, third, and fourth transistors 34, 36,38, and 40, respectively. The control module 32 charges the firstinductor 42 by setting the third and fourth control signals U₁ and D₁,respectively, high (or low) and discharges the first inductor 42 bysetting the third and fourth control signals U₁ and D₁, respectively,low (or high).

The control module 32 charges the second inductor 44 by setting thefirst and second control signals U₂ and D₂, respectively, high (or low)and discharges the second inductor 44 by setting the first and secondcontrol signals U₂ and D₂, respectively, low (or high). Based on afrequency and duty cycle of the control signals, the DC/DC converter 30transforms the input DC voltage 52 into the output DC voltage 54, whichis at a different level than the input DC voltage 52.

Referring now to FIG. 3, signal waveforms of the third and fourthcontrol signals U₁ and D₁, respectively, indicated by 62, and of thefirst and second control signals U₂ and D₂, respectively, indicated by64, are shown as square waveforms. The control module 32 maintains thesignal waveforms for the first, second, third, and fourth controlsignals U₂, D₂, U₁, and D₁, respectively, at a predetermined frequencyand duty cycle so that the DC/DC converter 30 generates a desiredvoltage. Signal waveforms 62 of the third and fourth control signals U₁and D₁, respectively, are complementary (or 180 degrees out-of-phase) tothe signal waveforms 64 of the first and second control signals U₂ andD₂, respectively. Therefore, when the first inductor 42 charges, thesecond inductor 44 discharges. Likewise, when the first inductor 42discharges, the second inductor 44 charges.

An advantage of the open-loop control system 28 of FIG. 2 is that theDC/DC converter 30 has a high efficiency and generates a small voltageripple. The DC/DC converter 30 also has a relatively fast response,which allows the capacitor 48 to be smaller in size. Additionally, thecontrol module 32 maintains the signal waveforms of the first, second,third, and fourth control signals U₂, D₂, U₁, and D₁, respectively, at afixed frequency and duty cycle. Therefore, no additional control isrequired for the open-loop control system 28 during normal operations.

However, there are advantages to allowing the phases of the signalwaveforms for the third and fourth control signals U₁ and D₁,respectively, and the first and second control signals U₂ and D₂,respectively, to overlap for a controlled period of time. For example,allowing same-phase operation of the control signals for a controlledperiod of time reduces the size of the effective inductor and produces amuch faster response in the DC/DC converter 30. This allows thecapacitor 48 to be even smaller in size. However, if same-phaseoperation of the control signals continues for too long, too muchcurrent may be charged in the first and second inductors 42 and 44,respectively, which adversely affects performance of the DC/DC converter30. Therefore, it is necessary to determine under which conditionssame-phase operation of the control signals is initiated and for howlong.

Referring now to FIG. 4, a closed-loop control system 72 for the DC/DCconverter 30 according to the present invention is shown. An input ofthe control module 32 receives the output DC voltage 54 of the DC/DCconverter 30. The control module 32 also optionally receives voltagesignals V_(x) ₁ and V_(x) ₂ from the first and second inductors 42 and44, respectively. For example, the control module 32 may perform acurrent estimation based on voltage signals V_(x) ₁ and V_(x) ₂ to sensea balance of the first and second inductors 42 and 44, respectively.

The control module 32 ensures that the phases of the signal waveformsfor the third and fourth control signals U₁ and D₁, respectively, arecomplementary to the phases of the signal waveforms for the first andsecond control signals U₂ and D₂, respectively, during normaloperations. The control module 32 initiates same-phase operation of thecontrol signals when a large voltage or current transient is detected inthe DC/DC converter 30 based on the output DC voltage 54.

In an exemplary embodiment, the control module 32 initiates same-phaseoperation of the control signals when a value of the output DC voltage54 is outside of a predetermined range. For example, the control module32 sets the signal waveforms of the control signals low (or high) whenthe value of the output DC voltage 54 is greater than a firstpredetermined voltage. This allows both the first and second inductors42 and 44, respectively, to discharge. The control module 32 sets thesignal waveforms of the control signals high (or low) when the value ofthe output DC voltage 54 is less than a second predetermined voltage.This allows both the first and second inductors 42 and 44, respectively,to charge.

The control module 32 may revert back to complementary operation of thecontrol signals when the value of the output DC voltage 54 is backwithin the predetermined range. Alternatively, the control module 32 mayrevert back to complementary operation of the control signals after apredetermined time period. In an exemplary embodiment, the predeterminedtime period is a function of one or more circuit conditions such as acurrent or voltage magnitude within the DC/DC converter 30.

In the event that the output DC voltage 54 is within the predeterminedrange, the current, I_(c), flowing through the capacitor 48 may still betoo high or too low. Therefore, in another exemplary embodiment, thecontrol module 32 initiates same-phase operation of the control signalswhen a value of the current flowing through the capacitor 48 is outsideof a predetermined range. For example, the control module 32 sets thesignal waveforms of the control signals low (or high) when the currentflowing through the capacitor 48 is greater than a first predeterminedcurrent. This allows both the first and second inductors 42 and 44,respectively, to discharge.

The control module 32 sets the signal waveforms of the control signalshigh (or low) when the current flowing through the capacitor 48 is lessthan a second predetermined current. This allows both the first andsecond inductors 42 and 44, respectively, to charge. As in the case ofthe voltage threshold, the control module 32 may revert back tocomplementary operation of the control signals when the current flowingthrough the capacitor 48 is back within the predetermined range.Alternatively, the control module 32 may revert back to complementaryoperation of the control signals after a predetermined time period.

Referring now to FIG. 5, the control module 32 estimates the current,I_(c), flowing through the capacitor 48 based on the output DC voltage54, V_(out). The current flowing through the capacitor 48 isproportional to the rate of change of the output DC voltage 54.Therefore, the control module 32 computes the amount of time, T_(cross),that it takes for the output DC voltage 54, indicated by 80, to increaseor decrease from a first predetermined voltage (V_(L) ₂ or V_(L) ₁ ) toa second predetermined voltage (V_(L) ₁ or V_(L) ₂ ). In the exemplaryembodiment illustrated in FIG. 5, the output DC voltage 54 decreasesfrom a first predetermined voltage (V_(L) ₁ ), indicated by 82, to asecond predetermined voltage (V_(L) ₂ ), indicated by 84.

As the value of T_(cross) decreases, the slope of V_(out) increases,which corresponds to an increase in the current flowing through thecapacitor 48. Likewise, as the value of T_(cross) increases, the slopeof V_(out) decreases, which corresponds to a decrease in the currentflowing through the capacitor 48. Therefore, by comparing T_(cross) to apredetermined time period, the control module 32 determines when thecurrent flowing through the capacitor 48 is outside of the predeterminedrange. Alternatively, the control module 32 may estimate the currentflowing through the capacitor 48 based on an average value of V_(out)during a predetermined time period.

Referring now to FIG. 6, the phase of the signal waveforms for the thirdand fourth control signals U₁ and D₁, respectively, indicated at 92,overlaps the phase of the signal waveforms for the first and secondcontrol signals U₂ and D₂, respectively, indicated at 94, for acontrolled period of time, T_(overlap). The T_(overlap) periodidentifies when the control module 32 maintains same-phase operation ofthe control signals. Before and after the T_(overlap) period, thecontrol module 32 maintains complementary operation of the controlsignals.

Referring now to FIG. 7, the control module 32 and the DC/DC converter30 are illustrated in further detail. Similar reference numbers are usedto identify elements as in FIG. 2. The control module 32 includes avoltage compare module 102 and a control signal generator 104. Thecontrol module 32 also optionally includes a current detection module106. A first input of the voltage compare module 102 receives the outputDC voltage 54 from the DC/DC converter 30. A second input of the voltagecompare module 102 receives a predetermined voltage. The voltage comparemodule 102 compares the output DC voltage 54 and the predeterminedvoltage to determine when the output DC voltage 54 is greater than orless than the predetermined voltage.

The voltage compare module 102 outputs the result to the control signalgenerator 104. Inputs of the optional current detection module 106receive the voltage signals V_(x) ₁ and V_(x) ₂ from the first andsecond inductors 42 and 44, respectively. The current detection module106 computes the difference between V_(x) ₁ and V_(x) ₂ and transmitsthe difference to the control signal generator 104. The control signalgenerator 104 generates the first, second, third, and fourth controlsignals U₂, D₂, U₁ and D₁, respectively, based on values of the controlsignals from the voltage compare module 102 and/or the current detectionmodule 106. The control signal generator 104 transmits the first,second, third, and fourth control signals U₂, D₂, U₁ and D₁,respectively, to the gates of the first, second, third, and fourthtransistors 34, 36, 38, and 40, respectively, in the DC/DC converter 30.

Referring now to FIG. 8, a first closed-loop control algorithm begins instep 114. In step 116, control reads the value of the output DC voltage54 from the DC/DC converter 30. In step 118, control determines whetherthe output DC voltage 54 is greater than a first predetermined voltageplus a threshold. If true, control proceeds to step 120. If false,control proceeds to step 122. In step 120, control initiates same-phaseoperation of the control signals by setting the signal waveforms of thecontrol signals low (or high). In step 124, control resets a timer. Instep 126, control determines whether the timer has expired. If false,control loops to step 126. If true, control proceeds to step 128.

In step 128, the control module 32 reverts back to complementaryoperation of the control signals and control ends. In step 122, controldetermines whether the output DC voltage 54 is less than a secondpredetermined voltage minus a threshold. For example, the thresholds insteps 118 and 122 may be equal and/or the first and second predeterminedvoltages may be equal. If true, control proceeds to step 130. If false,control proceeds to step 132. In step 130, the control module 32initiates same-phase operation of the control signals by setting thesignal waveforms of the control signals high (or low) and controlproceeds to step 124.

In step 132, the control module 32 estimates the current flowing throughthe capacitor 48 in the DC/DC converter 30. In step 134, controldetermines whether the current flowing through the capacitor 48 isgreater than a first predetermined current. If true, control proceeds tostep 120. If false, control proceeds to step 136. In step 136, controldetermines whether the current flowing through the capacitor 48 is lessthan a second predetermined current. For example, the secondpredetermined current may be equal in magnitude to the firstpredetermined current and have an opposite polarity. If true, controlproceeds to step 130. If false, control ends.

Referring now to FIG. 9, a second closed-loop control algorithm beginsin step 144. In step 146, control reads the value of the output DCvoltage 54 from the DC/DC converter 30. In step 148, control determineswhether the output DC voltage 54 is greater than a first predeterminedvoltage plus a threshold. If true, control proceeds to step 150. Iffalse, control proceeds to step 152. In step 150, the control module 32initiates same-phase operation of the control signals by setting thesignal waveforms of the control signals low (or high). In step 154,control determines whether the output DC voltage 54 is less than thefirst predetermined voltage plus the threshold. Is false, control loopsto step 154. If true, control proceeds to step 156. In step 156, thecontrol module 32 reverts back to complementary operation of the controlsignals and control ends.

In step 152, control determines whether the output DC voltage 54 is lessthan a second predetermined voltage minus a threshold. For example, thethresholds in steps 148 and 152 may be equal and/or the first and secondpredetermined voltages may be equal. If true, control proceeds to step158. If false, control proceeds to step 160. In step 158, the controlmodule 32 initiates same-phase operation of the control signals bysetting the signal waveforms of the control signals high (or low). Instep 162, control determines whether the output DC voltage 54 is greaterthan the second predetermined voltage minus the threshold. If false,control loops to step 162. If true, control proceeds to step 156. Instep 160, the control module 32 estimates the current flowing throughthe capacitor 48 in the DC/DC converter 30.

In step 164, control determines whether the current flowing through thecapacitor 48 is greater than a first predetermined current. If true,control proceeds to step 166. If false, control proceeds to step 168. Instep 166, the control module 32 initiates same-phase operation of thecontrol signals by setting the signal waveforms of the control signalslow (or high). In step 170, control determines whether the currentflowing through the capacitor 48 is less than the first predeterminedcurrent. If false, control loops to step 170. If true, control proceedsto step 156.

In step 168, control determines whether the current flowing through thecapacitor 48 is less than a second predetermined current. For example,the second predetermined current may be equal in magnitude to the firstpredetermined current and have an opposite polarity. If false, controlends. If true, control proceeds to step 172. In step 172, the controlmodule 32 initiates same-phase operation of the control signals bysetting the signal waveforms of the control signals high (or low). Instep 174, control determines whether the current flowing through thecapacitor 48 is greater than the second predetermined current. If false,control loops to step 174. If true, control proceeds to step 156.

The present invention allows for closed-loop digital control of acoupled-inductor DC/DC converter 30. However, the methods of the presentinvention may also be employed to control other electronic circuits of asimilar nature. By utilizing an output voltage feedback path, thecontrol module 32 is capable of detecting large voltage or currenttransients in the circuitry of the DC/DC converter 30. Therefore, theprevious constraint of constant complementary operation of the controlsignals is relaxed. This allows the DC/DC converter 30 to achieve aneven faster response and requires an even smaller output capacitor 48than DC/DC converters that employ open-loop control systems.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, specification, and the following claims.

1. A control system, comprising: a DC/DC converter including a firstinductor and a second inductor, the DC/DC converter configured to i)receive a first DC voltage and ii) output a second DC voltage; and acontrol module configured to during a first operation mode, charge thefirst inductor while discharging the second inductor, during a secondoperation mode, one of i) charge the first inductor while charging thesecond inductor and ii) discharge the first inductor while dischargingthe second inductor, and initiate the second operation mode in responseto detecting a current transient in the DC/DC converter.
 2. The controlsystem of claim 1, wherein the control module is configured to: chargethe first inductor while charging the second inductor in response to thesecond DC voltage being greater than a first predetermined voltage; anddischarge the first inductor while discharging the second inductor inresponse to the second DC voltage being less than a second predeterminedvoltage.
 3. The control system of claim 1, wherein the control module isconfigured to estimate the current transient in response to the secondDC voltage being outside of a predetermined range.
 4. The control systemof claim 3, wherein: subsequent to initiating the second operation mode,the control module is configured to transition back to the firstoperation mode in response to the second DC voltage returning to thepredetermined range.
 5. The control system of claim 3, wherein:subsequent to initiating the second operation mode, the control moduleis configured to transition back to the first operation mode after apredetermined time period.
 6. The control system of claim 1, furthercomprising: an output capacitor, wherein the control module isconfigured to detect the current transient based on a current throughthe output capacitor.
 7. The control system of claim 6, wherein thecontrol module is configured to: discharge the first inductor whiledischarging the second inductor in response to the current being greaterthan a first predetermined current; and charge the first inductor whilecharging the second inductor in response to the current being less thana second predetermined current.
 8. The control system of claim 6,wherein the control module is configured to initiate the secondoperation mode in response to the current being outside of apredetermined range.
 9. The control system of claim 8, wherein:subsequent to initiating the second operation mode, the control moduleis configured to transition back to the first operation mode in responseto the current returning to the predetermined range.
 10. The controlsystem of claim 8, wherein: subsequent to initiating the secondoperation mode, the control module is configured to transition back tothe first operation mode after a predetermined time period.
 11. Thecontrol system of claim 1, wherein the control module is configured todetect the current transient based on a rate of change of the second DCvoltage.
 12. The control system of claim 11, wherein the control moduleis configured to: compute a time it takes for the second DC voltage tochange from a first predetermined voltage to a second predeterminedvoltage; perform a comparison of the time to a predetermined timeperiod; and detect the current transient based on the comparison. 13.The control system of claim 1 wherein the control module is configuredto detect the current transient based on an average value of the secondDC voltage during a predetermined time period.
 14. A method foroperating control system, the method comprising: receiving, at a DC/DCconverter, a first DC voltage, wherein the DC/DC converter includes afirst inductor and a second inductor; outputting, at the DC/DCconverter, a second DC voltage; during a first operation mode, chargingthe first inductor while discharging the second inductor; during asecond operation mode, one of i) charging the first inductor whilecharging the second inductor and ii) discharging the first inductorwhile discharging the second inductor; and initiating the secondoperation mode in response to detecting a current transient in the DC/DCconverter.
 15. The method of claim 14, further comprising: charging thefirst inductor while charging the second inductor in response to thesecond DC voltage being greater than a first predetermined voltage; anddischarging the first inductor while discharging the second inductor inresponse to the second DC voltage being less than a second predeterminedvoltage.
 16. The method of claim 14, further comprising: detecting thecurrent transient based on current through an output capacitor of theDC/DC converter.
 17. The method of claim 16, further comprisingdischarging the first inductor while discharging the second inductor inresponse to the current being greater than a first predeterminedcurrent; and charging the first inductor while charging the secondinductor in response to the current being less than a secondpredetermined current.
 18. The method of claim 14, further comprisingdetecting the current transient based on a rate of change of the secondDC voltage.
 19. The method of claim 18, further comprising: computing atime it takes for the second DC voltage to change from a firstpredetermined voltage to a second predetermined voltage; comparing thetime to a predetermined time period; and detecting the current transientbased on the comparison.